Are Drier Times Ahead?

Have Americans grown used to an overabundance of rain? Scientists at the

Agricultural Research Service's Grazinglands Research Laboratory in El Reno,

Okla., think so. They want everyone involved in water management today to

prepare for normal, drier precipitation patterns.

Soil scientist Jean Steiner warns that drier conditions would increasingly

stress water-supply systems, causing water-usage conflicts. She adds that

management strategies that account for precipitation variations--and use the

latest technologies--should be developed.

One aspect Steiner and her colleagues--hydraulic engineer Jurgen Garbrecht

and hydrologists Michael W. Van Liew and John X. Zhang--are focusing on is

how computer-generated seasonal forecasts and precipitation-trend data can

be tailored to help gauge long-term effects of drier conditions on

streamflow and water supplies.

Garbrecht and Schneider studied National Oceanic and Atmospheric

Administration records from 1895 to 2001 and found that precipitation over

the United States from 1971 to 2000 was about four percent higher than

during the entire period studied. It's now been drier over the past couple

of years, something the researchers see as perhaps the start of a new trend.

One study, by Van Liew, showed how reliance on abundant rainfall can lead to

problems in drier times. When precipitation in an Oklahoma creek was 20

percent greater than average, streamflow increased by 39 percent; but when

precipitation was 40 percent greater than average, streamflow increased by

96 percent.

Meanwhile, Zhang related this research directly to agriculture by using

seasonal climate forecasts and climate-change projections to measure the

effects of short- and long-range variations on water runoff, soil erosion

and winter wheat production. He took actual changes in precipitation and

temperatures between 1950 and 1999, and those projected for 2056 to 2085,

and constructed five climate-change scenarios showing how soil erosion and

crop production may change if various climate factors change.